1. Field of the Invention
The present invention relates generally to an apparatus and method for automatically supplying insulin based on the amount of a user's exercise.
2. Description of the Related Art
In general, a diabetic patient does not have a sufficient or normal ability to produce insulin that controls his or her blood sugar. Thus, an insulin injection and/or a special diet help stabilize the blood sugar of a diabetic patient. To continuously supply insulin at a level similar to that of normal pancreatic function, an insulin pump is used.
A decision is made as to whether to inject insulin based on a blood sugar measurement. Normal blood sugar levels range from approximately 70 to 140 milligrams/deciLiter (mg/dL) before and after a meal. Hypoglycemia is defined as a blood sugar level of 70 mg/dL or below. If a diabetic patient's blood sugar is 200 mg/dL or higher, sugar appears in his or her urine. If the blood sugar level reaches 400 mg/dL or higher, an insulin injection is needed. According to a current insulin injection procedure, blood sugar levels are measured before and after a meal and compared with a normal blood sugar range. It is then determined whether to inject insulin based on the comparison. If it is determined that the patient requires insulin, a dose of a required amount of insulin is administered.
An insulin pump injects a preset dose of insulin based on a manual setting. The dose of insulin does not reflect an improvement in a patient's health. That is, the patient's blood sugar level is simply reduced in an artificial manner by injection of an appropriate dose of insulin at each meal.
As described above, the administered dose of insulin should be adjusted for a diabetic patient. Although the same dose of insulin is administered to a diabetic patient every day, the dose of insulin should be adjusted based on meals, physical activity, blood sugar, etc. Thus, an insulin injection may not need to occur regularly. While a change in blood sugar is mostly attributed to eating, an insulin injection is necessary in some cases, for example, when the diabetic patient experiences a rapid change in the amount of exercise or pulse for an unspecified reason.
For instance, when a diabetic patient is exercising, adrenalin production increases from the workout, thus raising a blood sugar level. The blood sugar level rapidly drops after the exercise. Accordingly, if the diabetic patient experiences a change in blood sugar due to unplanned exercise, it is difficult to determine whether the change of blood sugar is caused by a meal or exercise. Therefore, when the blood sugar begins to rise due to exercise, an insulin pump injects insulin, incorrectly assuming that the diabetic patient is eating. As a result, both the post-exercise blood sugar reduction and insulin effects may cause a rapid drop in blood sugar, thereby leading to hypoglycemia.
As a preset dose of insulin is injected unconditionally to a diabetic patient irrespective of a change in blood sugar due to exercise, controlled injection of an appropriate dose of insulin is difficult. Therefore, there exists a need for a method for determining whether to inject insulin adaptively according to whether a patient is exercising.